The present invention contemplates an improved method and apparatus for controlling gasoline vapor emissions at a service station or stations where liquid gasoline is transferred from one container or tank to another. The invention particularly relates to certain modifications and improvements in the apparatus and method of abatement of vapor emissions as described in U.S. Pat. Nos. 4,009,985; 4,118,170; and 4,292,020 owned by a common assignee.
Generally speaking the above three patents disclose an apparatus and method for controlling vapor emissions wherein the system preferably operates under a slight vacuum, is arranged to permit collected gasoline vapors in the system to recondense in the underground vapor storage containers, provides saturated vapors to blanket the stored liquid gasoline from air, thus preventing further evaporation of gasoline, provides vapors to replace gasoline dispensed, suppresses the formation of excess vapors, and thermally oxidizes any excess vapors in the system into carbon dioxide and water vapors which are clean, odorless, invisible and nonpolluting. Such patents describe multistage and single stage burners for disposing of the vapors, each burner being adapted to operate under certain specified conditions. The above three patents describe service station vapor emission conditions in detail and such description and subject matter of said patents are incorporated herein by reference.
In each of the above three patents the vapor emission control system described and included the use of compressed air which is readily available at a gasoline service station. However, the quality of the compressed air available at the many different gasoline service stations throughout the country was not uniform and in the past several years has significantly deteriorated. Such deterioration includes the presence of dirt, oil and water in the compressed air which, when used with a vapor emission controlled system utilizing compressed air, affected the vapor control system as described in the aforesaid three patents, compressed air from an air compressor was directed to an ejector where the compressed air through the ejector venturi created a vacuum and caused flow of vapor. Such flow of vapor induced by the compressed air created a vacuum in the vapor piping system of the service station, such vapor piping system including the vapor lines from the gasoline dispenser, the air space above the liquid level in the storage tanks, and the vent pipes for venting the tanks to atmosphere. In addition, in U.S. Pats. Nos. 4,292,020 and 4,118,170 compressed air and its presence in the system was required for actuation of valves opening the main flow of vapor to the main burner.
Further, since each gasoline service station is characterized by its own particular installation and in which distances between the gasoline dispensers and the gasoline storage containers and to the disposal means may vary and since such piping and fittings may develop underground difficult to locate air leaks, the mixture of the compressed air with a lean vapor mixture in the vapor piping system to provide a combustible mixture was sometimes difficult to obtain since the addition of compressed air to the already lean vapor mixture might result in a still leaner mixture which may or may not be combustible.